Category Archives: Quantum Physics

Physicists have discovered a jewel-like geometric object that dramatically simplifies calculations of particle interactions and challenges the notion that space and time are fundamental components of reality.

This is completely new and very much simpler than anything that has been done before, said Andrew Hodges, a mathematical physicist at Oxford University who has been following the work.

The revelation that particle interactions, the most basic events in nature, may be consequences of geometry significantly advances a decades-long effort to reformulate quantum field theory, the body of laws describing elementary particles and their interactions. Interactions that were previously calculated with mathematical formulas thousands of terms long can now be described by computing the volume of the corresponding jewel-like amplituhedron, which yields an equivalent one-term expression.

The degree of efficiency is mind-boggling, said Jacob Bourjaily, a theoretical physicist at Harvard University and one of the researchers who developed the new idea. You can easily do, on paper, computations that were infeasible even with a computer before.

The new geometric version of quantum field theory could also facilitate the search for a theory of quantum gravity that would seamlessly connect the large- and small-scale pictures of the universe. Attempts thus far to incorporate gravity into the laws of physics at the quantum scale have run up against nonsensical infinities and deep paradoxes. The amplituhedron, or a similar geometric object, could help by removing two deeply rooted principles of physics: locality and unitarity.

Both are hard-wired in the usual way we think about things, said Nima Arkani-Hamed, a professor of physics at the Institute for Advanced Study in Princeton, N.J., and the lead author of the new work, which he is presenting in talks and in a forthcoming paper. Both are suspect.

Locality is the notion that particles can interact only from adjoining positions in space and time. And unitarity holds that the probabilities of all possible outcomes of a quantum mechanical interaction must add up to one. The concepts are the central pillars of quantum field theory in its original form, but in certain situations involving gravity, both break down, suggesting neither is a fundamental aspect of nature.

In keeping with this idea, the new geometric approach to particle interactions removes locality and unitarity from its starting assumptions. The amplituhedron is not built out of space-time and probabilities; these properties merely arise as consequences of the jewels geometry. The usual picture of space and time, and particles moving around in them, is a construct.

Its a better formulation that makes you think about everything in a completely different way, said David Skinner, a theoretical physicist at Cambridge University.

The amplituhedron itself does not describe gravity. But Arkani-Hamed and his collaborators think there might be a related geometric object that does. Its properties would make it clear why particles appear to exist, and why they appear to move in three dimensions of space and to change over time.

Because we know that ultimately, we need to find a theory that doesnt have unitarity and locality, Bourjaily said, its a starting point to ultimately describing a quantum theory of gravity.

The amplituhedron looks like an intricate, multifaceted jewel in higher dimensions. Encoded in its volume are the most basic features of reality that can be calculated, scattering amplitudes, which represent the likelihood that a certain set of particles will turn into certain other particles upon colliding. These numbers are what particle physicists calculate and test to high precision at particle accelerators like the Large Hadron Collider in Switzerland.

The 60-year-old method for calculating scattering amplitudes a major innovation at the time was pioneered by the Nobel Prize-winning physicist Richard Feynman. He sketched line drawings of all the ways a scattering process could occur and then summed the likelihoods of the different drawings. The simplest Feynman diagrams look like trees: The particles involved in a collision come together like roots, and the particles that result shoot out like branches. More complicated diagrams have loops, where colliding particles turn into unobservable virtual particles that interact with each other before branching out as real final products. There are diagrams with one loop, two loops, three loops and so on increasingly baroque iterations of the scattering process that contribute progressively less to its total amplitude. Virtual particles are never observed in nature, but they were considered mathematically necessary for unitarity the requirement that probabilities sum to one.

The number of Feynman diagrams is so explosively large that even computations of really simple processes werent done until the age of computers, Bourjaily said. A seemingly simple event, such as two subatomic particles called gluons colliding to produce four less energetic gluons (which happens billions of times a second during collisions at the Large Hadron Collider), involves 220 diagrams, which collectively contribute thousands of terms to the calculation of the scattering amplitude.

In 1986, it became apparent that Feynmans apparatus was a Rube Goldberg machine.

To prepare for the construction of the Superconducting Super Collider in Texas (a project that was later canceled), theorists wanted to calculate the scattering amplitudes of known particle interactions to establish a background against which interesting or exotic signals would stand out. But even 2-gluon to 4-gluon processes were so complex, a group of physicists had written two years earlier, that they may not be evaluated in the foreseeable future.

Stephen Parke and Tomasz Taylor, theorists at Fermi National Accelerator Laboratory in Illinois, took that statement as a challenge. Using a few mathematical tricks, they managed to simplify the 2-gluon to 4-gluon amplitude calculation from several billion terms to a 9-page-long formula, which a 1980s supercomputer could handle. Then, based on a pattern they observed in the scattering amplitudes of other gluon interactions, Parke and Taylor guessed a simple one-term expression for the amplitude. It was, the computer verified, equivalent to the 9-page formula. In other words, the traditional machinery of quantum field theory, involving hundreds of Feynman diagrams worth thousands of mathematical terms, was obfuscating something much simpler. As Bourjaily put it: Why are you summing up millions of things when the answer is just one function?

We knew at the time that we had an important result, Parke said. We knew it instantly. But what to do with it?

The message of Parke and Taylors single-term result took decades to interpret. That one-term, beautiful little function was like a beacon for the next 30 years, Bourjaily said. It really started this revolution.

In the mid-2000s, more patterns emerged in the scattering amplitudes of particle interactions, repeatedly hinting at an underlying, coherent mathematical structure behind quantum field theory. Most important was a set of formulas called the BCFW recursion relations, named for Ruth Britto, Freddy Cachazo, Bo Feng and Edward Witten. Instead of describing scattering processes in terms of familiar variables like position and time and depicting them in thousands of Feynman diagrams, the BCFW relations are best couched in terms of strange variables called twistors, and particle interactions can be captured in a handful of associated twistor diagrams. The relations gained rapid adoption as tools for computing scattering amplitudes relevant to experiments, such as collisions at the Large Hadron Collider. But their simplicity was mysterious.

The terms in these BCFW relations were coming from a different world, and we wanted to understand what that world was, Arkani-Hamed said. Thats what drew me into the subject five years ago.

With the help of leading mathematicians such as Pierre Deligne, Arkani-Hamed and his collaborators discovered that the recursion relations and associated twistor diagrams corresponded to a well-known geometric object. In fact, as detailed in a paper posted to arXiv.org in December by Arkani-Hamed, Bourjaily, Cachazo, Alexander Goncharov, Alexander Postnikov and Jaroslav Trnka, the twistor diagrams gave instructions for calculating the volume of pieces of this object, called the positive Grassmannian.

Named for Hermann Grassmann, a 19th-century German linguist and mathematician who studied its properties, the positive Grassmannian is the slightly more grown-up cousin of the inside of a triangle, Arkani-Hamed explained. Just as the inside of a triangle is a region in a two-dimensional space bounded by intersecting lines, the simplest case of the positive Grassmannian is a region in an N-dimensional space bounded by intersecting planes. (N is the number of particles involved in a scattering process.)

It was a geometric representation of real particle data, such as the likelihood that two colliding gluons will turn into four gluons. But something was still missing.

The physicists hoped that the amplitude of a scattering process would emerge purely and inevitably from geometry, but locality and unitarity were dictating which pieces of the positive Grassmannian to add together to get it. They wondered whether the amplitude was the answer to some particular mathematical question, said Trnka, a post-doctoral researcher at the California Institute of Technology. And it is, he said.

Arkani-Hamed and Trnka discovered that the scattering amplitude equals the volume of a brand-new mathematical object the amplituhedron. The details of a particular scattering process dictate the dimensionality and facets of the corresponding amplituhedron. The pieces of the positive Grassmannian that were being calculated with twistor diagrams and then added together by hand were building blocks that fit together inside this jewel, just as triangles fit together to form a polygon.

Like the twistor diagrams, the Feynman diagrams are another way of computing the volume of the amplituhedron piece by piece, but they are much less efficient. They are local and unitary in space-time, but they are not necessarily very convenient or well-adapted to the shape of this jewel itself, Skinner said. Using Feynman diagrams is like taking a Ming vase and smashing it on the floor.

Arkani-Hamed and Trnka have been able to calculate the volume of the amplituhedron directly in some cases, without using twistor diagrams to compute the volumes of its pieces. They have also found a master amplituhedron with an infinite number of facets, analogous to a circle in 2-D, which has an infinite number of sides. Its volume represents, in theory, the total amplitude of all physical processes. Lower-dimensional amplituhedra, which correspond to interactions between finite numbers of particles, live on the faces of this master structure.

They are very powerful calculational techniques, but they are also incredibly suggestive, Skinner said. They suggest that thinking in terms of space-time was not the right way of going about this.

The seemingly irreconcilable conflict between gravity and quantum field theory enters crisis mode in black holes. Black holes pack a huge amount of mass into an extremely small space, making gravity a major player at the quantum scale, where it can usually be ignored. Inevitably, either locality or unitarity is the source of the conflict.

We have indications that both ideas have got to go, Arkani-Hamed said. They cant be fundamental features of the next description, such as a theory of quantum gravity.

String theory, a framework that treats particles as invisibly small, vibrating strings, is one candidate for a theory of quantum gravity that seems to hold up in black hole situations, but its relationship to reality is unproven or at least confusing. Recently, a strange duality has been found between string theory and quantum field theory, indicating that the former (which includes gravity) is mathematically equivalent to the latter (which does not) when the two theories describe the same event as if it is taking place in different numbers of dimensions. No one knows quite what to make of this discovery. But the new amplituhedron research suggests space-time, and therefore dimensions, may be illusory anyway.

We cant rely on the usual familiar quantum mechanical space-time pictures of describing physics, Arkani-Hamed said. We have to learn new ways of talking about it. This work is a baby step in that direction.

Even without unitarity and locality, the amplituhedron formulation of quantum field theory does not yet incorporate gravity. But researchers are working on it. They say scattering processes that include gravity particles may be possible to describe with the amplituhedron, or with a similar geometric object. It might be closely related but slightly different and harder to find, Skinner said.

Physicists must also prove that the new geometric formulation applies to the exact particles that are known to exist in the universe, rather than to the idealized quantum field theory they used to develop it, called maximally supersymmetric Yang-Mills theory. This model, which includes a superpartner particle for every known particle and treats space-time as flat, just happens to be the simplest test case for these new tools, Bourjaily said. The way to generalize these new tools to [other] theories is understood.

Beyond making calculations easier or possibly leading the way to quantum gravity, the discovery of the amplituhedron could cause an even more profound shift, Arkani-Hamed said. That is, giving up space and time as fundamental constituents of nature and figuring out how the Big Bang and cosmological evolution of the universe arose out of pure geometry.

In a sense, we would see that change arises from the structure of the object, he said. But its not from the object changing. The object is basically timeless.

While more work is needed, many theoretical physicists are paying close attention to the new ideas.

The work is very unexpected from several points of view, said Witten, a theoretical physicist at the Institute for Advanced Study. The field is still developing very fast, and it is difficult to guess what will happen or what the lessons will turn out to be.

Note: This article was updated on December 10, 2013, to include a link to the first in a series of papers on the amplituhedron.

This article was reprinted on Wired.com.

See the article here:

Physicists Discover Geometry Underlying Particle Physics

A recent argument has popped up suggesting that Ant-Man is quite possibly Marvels most deadly superhero, and that he could defeat DCs Superman if the full extent of his abilities were realized. But does it hold up upon closer examination of understanding the wacky world of comic book physics?

Inverse recently had a talk with Dr. Spiros Michalakis, who served as a scientific consultant on Marvels 2015 sleeper hitAnt-Man. The scientistpreviously wrote the following back in 2015 right after the release of the film:

If someone could go to a place where the laws of physics as we know them were not yet formed, at a place where the arrow of time was broken and the fabric of space was not yet woven, the powers of such a master of the quantum realm would only be constrained by their ability to come back to the same (or similar) reality from which they departed. All the superheroes of Marvel and DC Comics combined would stand no chance against Ant-Man with a malfunctioning regulator.

More recently, Dr. Michalakis expanded upon his original thesis when he wrote back to Inverse.

What Im saying is that potentially understanding the quantum code from which curvature of space-time comes from, [Ant-Man] could manipulate to increase it or decrease it. Ant-Man could have created say, a black hole. Could Superman escape the black hole? Probably not. Then game over.

So at face value, Ant-Man could win by fundamentally altering the basic values of quantum physics a fair assumption to make under normal circumstances, as with those kinds of powers, the character could probably beat the vast majority of comic book characters across multiple fictional universes. Im no scientist, but Id like to take a shot at playing devils advocate here. In such a scenario, Ant-Man probably could take on a number of superheroes without issues and win every time by more-or-less Doctor Manhattan-ing his way through existence. But the thing is that were talking about God-Mode Ant-Man going up against Superman, and Supermans no slouch when it comes to messing with the laws of physics as well, in part because, at his core, Superman is meant to be a character free from all limitations at his absolute best even though hes only as strong as the story needs him to be. A story could necessitate that hed get stuck in a black hole, while another would say he could escape.

Among some of Kal-Els greatest science-defying feats include the ability to hold a personification of Infinity (an object thats so massive that it should be completely impossible within any given Universe), hearing emergency signals light-years away from the source and getting back there in a matter of minutes (something which is impossible because sound cant be transmitted through space, as is traveling faster than light without tearing a hole in reality), and obliterating the New God Darkseid from the Universe by singing. (Seriously, all of that happened Post-Crisis.) And thats allwiththe standard physical limitations of the DC Universe. Could you imagine how much more powerful you could potentially make Superman could be if you messed around with the quantum physicsof the Universe?

Admittedly, the article notes that there are limitations to this line of thought, which is something thats lost in the actual headline of the piece. Theres no indication that theres any version of Ant-Man, let alone the one weve seen in the MCU, has been able to cheese his way toward omnipotence, which is something the original article mentions. And thats also not getting into the fact that my explanation of Supermans impossible feats neglect to mention his weaknesses (Kryptonite and magic, among other things), nor do they mention that Supermans powers are entirely based on solar energy and that he could lose them if its blocked off either of which Ant-Man could exploit under the right circumstances. So yeah, Ant-Man probablycoulddestroy Superman in this kind of a situation, but one could just turn around and argue that Superman could find a way to defeat Ant-Man. In the end, I feel as though Im in agreement with Stan Lees position on the prospect of a different What If? battle the victor can only be decided by whomever is actually writing the story.

Superman (portrayed by Henry Cavill) will next be seen on film in this Autumns Justice Leagueand in a standalone Supermanfilm sometime after that. Ant-Man (portrayed by Paul Rudd) has yet to be confirmed for eitherAvengers: Infinity War or its sequel, but he will be returning in next years Ant-Man & The Wasp.

Source: Inverse

The DCEU has found its own definitive version of Superman. Henry Cavill has been given the opportunity to play the iconic superhero in this monster of a DC franchise and so far hes done a great job with the role and brining Superman into the new century in a new way. With Justice League set to hit theaters later this year its safe to say that we will be seeing a lot from him over the next several years. So far there have only been two movies featuring him but these two movies have already given us some memorable moments with the character. These moments in particular stand out and give a weight to the character that is crucial to this series continued success. While it still may be early its a good time to look back at said great moments.

Here are 5 of the Best DCEU Superman Moments So Far. Click Next to continue

Go here to read the rest:

Could Ant-Man Beat Superman With Quantum Physics? - Heroic Hollywood (blog)

Long before the days of internet cat videos, what was perhaps the original famous cat was born in the mind of Austrian physicist Erwin Schrdinger as an analogy to describe a foundational concept of quantum physics.

Schrdinger postulated a cat in a sealed box with a vial of poison that could be released by a random event such as a decaying radioactive particle. In this simplified view of quantum physics, the hypothetical cat is held in states of being alive and dead at the same time, until the box is opened to determine the cats state.

Now, 80 years later, Schrdingers cat may help describe a revolutionary technology future in the form of quantum computing. At 7 p.m. Tuesday, May 30, Nobel Prize-winning physicist David Wineland will give a free public lecture in Room 156, Straub Hall on his research into quantum phenomena and how it could lead to the most powerful computers ever created.

Its not every day we have the chance to hear a Nobel laureate explain the intricacies of quantum mechanics, said Michael Raymer, a professor in the Department of Physics. Were fortunate to have him visiting the UO.

Winelands talk, Quantum Computers and Schrdingers Cat, will delve into the strange world of quantum physics where all the rules of traditional physics seem to disappear a world that exists at the atomic level and is especially difficult to study.

Wineland is the founder of a research group focused on ion storage at the National Institute of Standards and Technology in Boulder, Colorado. His work at the institute and as a member of the physics faculty of the University of Colorado at Boulder has led to advances in spectroscopy, atomic clocks and quantum information. Winelands research showed that ideas previously thought of as purely theoretical can be tested and measured in the laboratory.

Wineland will discuss the work that led to his 2012 Nobel Prize, which he won along with French physicist Serge Haroche for groundbreaking experimental methods that enable measuring and manipulation of individual quantum systems.

These newly measured phenomena at the single-atom level are intimately tied to the hot-button topic of quantum computing, which is based on the idea that as computer chips pack more data into smaller spaces, the materials that store individual pieces of data get smaller too. When these materials become single atoms, physicists say, everything starts behaving differently than in ordinary computers, and the physics principle of superposition of distinct states is needed to understand what happens.

While this poses significant challenges, scientists say it also opens the door to incredible opportunities in the form of quantum computers. Current computers store information in bits as either a 1 or 0, but a quantum computer would store information in quantum bits, or qubits, which can be a superposition of both 1 and 0, much as the hypothetical cat can be a superposition of alive and dead. Although such quantum trickery cannot be carried out for a real cat, Raymer says superpositions for qubits are quite real phenomena and lead to the power of quantum computing.

Physicists acknowledge this is a tricky concept to grasp since the idea that something can simultaneously be two different things seems impossible. Yet, scientists worldwide are now racing to harness the simultaneous nature of qubits to store and process vastly more data than can be stored as a humble 1 or 0.

After such explanations, are you starting to feel like Schrdingers cat yourself, in a superposition of understanding and not understanding? Raymer said. Come to the lecture and David Wineland will help you understand.

Quantum Computers and Schrdingers Cat is sponsored by the Department of Physics, the Center for Optical, Molecular and Quantum Science, and the Office of the Vice President for Research and Innovation. For more information, visit the UOs Research and Innovation website.

By Stephanie Nappa, Office for Research and Innovation

Read more here:

Nobel winner to talk cats, computers and quantum physics - AroundtheO

In Brief Quantum physics could, theoretically, be used to fulfill the age old desire to teleport. However, any practical use is a an extremely long way off, with scientists only managing single particles so far.

In the video below,minutephysics explain how teleportation could be theoretically possible using quantum physics. Quantum teleportation uses quantum entanglement a situation where one set of particles is dependent on the state of another. In principle, if scientists create specific sets of particles that are capable of being rearranged into whatever they wish to teleport, they can send partial information about one end of the entanglement encoded as a quantum state and thereby produce it in the other end. As an analogy: imagine taking a scan of what you want to transport, sending it to the other entangled particles, and rebuilding it from that.

While being able to transport anything large, like a cat the example the video uses is a long way off, scientists have managed to transport a single photon or electron about 100km. The difficulty lies in creating two entangled sets of particles and subsequently transporting one of them without it becoming disentangled.

This is linked to scientists achieving direct counterfactual quantum communication for the first time recently, which operates using the Zeno effect (freezing the situation by observing it) rather than entanglement. In the experiment, scientists successfully transported information using the phase of light.

Follow this link:

Teleportation Could Be Possible Using Quantum Physics - Futurism - Futurism

A quantum test could tell us what minds are made of

Dominic Lipinski/PA

By Anil Ananthaswamy

The boundary between mind and matter could be tested using a new twist on a well-known experiment in quantum physics.

Over the past two decades, a type of experiment known as a Bell test has confirmed the weirdness of quantum mechanics specifically the spooky action at a distance that so bothered Einstein.

Now, a theorist proposes a Bell test experiment using something unprecedented: human consciousness. If such an experiment showed deviations from quantum mechanics, it could provide the first hints that our minds are potentially immaterial.

Spooky action at a distance was Einsteins phrase for a quantum effect called entanglement. If two particles are entangled, then measuring the state of one particle seems to instantly influence the state of the other, even if they are light years apart.

But any signal passing between them would have to travel faster than the speed of light, breaking the cosmic speed limit. To Einstein, this implied that quantum theory was incomplete, and that there was a deeper theory that could explain the particles behaviour without resorting to weird instantaneous influence. Some physicists have been trying to find this deeper theory ever since.

In 1964, physicist John Bell paved the way for testing whether the particles do in fact influence each other. He devised an experiment that involves creating a pair of entangled particles and sending one towards location A and the other to location B. At each point, there is a device that measures, say, the spin of the particle.

The setting on the device for example, whether to measure the particles spin in the +45 or -45 degree direction is chosen using random number generators, and in such a way that its impossible for A to know of Bs setting and vice-versa at the time of the measurement.

The measurements are done for numerous entangled pairs. If quantum physics is correct and there is indeed spooky action at a distance, then the results of these measurements would be correlated to a far greater extent than if Einstein was correct. All such experiments so far have supported quantum physics.

However, some physicists have argued that even the random number generators may not be truly random. They could be governed by some underlying physics that we dont yet understand, and this so-called super-determinism could explain the observed correlations.

Now, Lucien Hardy at the Perimeter Institute in Canada suggests that the measurements at A and B can be controlled by something that could potentially be separate from the material world: the human mind.

[French philosopher Rene] Descartes put forth this mind-matter duality, [where] the mind is outside of regular physics and intervenes on the physical world, says Hardy.

To test this idea, Hardy proposed an experiment in which A and B are set 100 kilometres apart. At each end, about 100 humans are hooked up to EEG headsets that can read their brain activity. These signals are then used to switch the settings on the measuring device at each location.

The idea is to perform an extremely large number of measurements at A and B and extract the small fraction in which the EEG signals caused changes to the settings at A and B after the particles departed their original position but before they arrived and were measured..

If the amount of correlation between these measurements doesnt tally with previous Bell tests, it implies a violation of quantum theory, hinting that the measurements at A and B are being controlled by processes outside the purview of standard physics.

[If] you only saw a violation of quantum theory when you had systems that might be regarded as conscious, humans or other animals, that would certainly be exciting. I cant imagine a more striking experimental result in physics than that, Hardy says. Wed want to debate as to what that meant.

Such a finding would stir up debate about the existence of free will. It could be that even if physics dictated the material world, the human mind not being made of that same matter would mean that we could overcome physics with free will. It wouldnt settle the question, but it would certainly have a strong bearing on the issue of free will, says Hardy.

Nicolas Gisin at the University of Geneva in Switzerland thinks Hardys proposal makes plenty of sense, but hes sceptical of using unstructured EEG signals to switch settings on devices. Thats akin to using the brain as a random number generator, says Gisin. He would rather see an experiment where the conscious intent of humans is used to perform the switching but that would be experimentally more challenging.

Either way, he wants to see the experiment done. There is an enormous probability that nothing special will happen, and that quantum physics will not change, says Gisin. But if someone does the experiment and gets a surprising result, the reward is enormous. It would be the first time we as scientists can put our hands on this mind-body or problem of consciousness.

Journal reference: arXiv, DOI: 1705.04620v1

More on these topics:

Read more:

A classic quantum test could reveal the limits of the human mind - New Scientist

Slide: 1 / of 1. Caption: Getty Images

At the Ludwig-Maximilian University of Munich, the basement of the physics building is connected to the economics building by nearly half a miles worth of optical fiber. It takes a photon three millionths of a secondand a physicist, about five minutesto travel from one building to the other. Starting in November 2015, researchers beamed individual photons between the buildings, over and over again for seven months, for a physics experiment that could one day help secure your data.

Their immediate goal was to settle a decades-old debate in quantum mechanics: whether the phenomenon known as entanglement actually exists. Entanglement, a cornerstone of quantum theory, describes a bizarre scenario in which the fate of two quantum particlessuch as a pair of atoms, or photons, or ionsare intertwined. You could separate these two entangled particles to opposite sides of the galaxy, but when you mess with one, you instantaneously change the other. Einstein famously doubted that entanglement was actually a thing and dismissed it as spooky action at a distance.

Over the years, researchers have run all sorts of complicated experiments to poke at the theory. Entangled particles exist in nature, but theyre extremely delicate and hard to manipulate. So researchers make them, often using lasers and special crystals, in precisely controlled settings to test that the particles behave the way prescribed by theory.

In Munich, researchers set about their test in two laboratories, one in the physics building, the other in economics. In each lab, they used lasers to coax a single photon out of a rubidium atom; according to quantum mechanics theory, colliding those two photons would entangle the rubidium atoms. That meant they had to get the atoms in both departments to emit a photon pretty much simultaneouslyaccomplished by firing a tripwire electric signal from one lab to the other. Theyre synchronized to less than a nanosecond, says physicist Harald Weinfurter of the Ludwig-Maximilian University of Munich.

The researchers collided the two photons by sending one of them over the optical fiber. Then they did it again. And again, tens of thousands of times, followed up by statistical analysis. Even though the atoms were separated by a quarter of a milealong with all the impinging buildings, roads, and treesthe researchers found the two particles properties were correlated. Entanglement exists.

So, quantum mechanics isnt broken which is exactly what the researchers expected. In fact, this experiment basically shows the same results as a series of similar tests that physicists started to run in 2015. Theyre known as Bell tests, named for John Stewart Bell, the northern Irish physicist whose theoretical work inspired them. Few physicists still doubt that entanglement exists. I dont think theres any serious or large-scale concern that quantum mechanics is going to be proven wrong tomorrow, says physicist David Kaiser of MIT, who wasnt involved in the research. Quantum theory has never, ever, ever let us down.

But despite their predictable results, researchers find Bell tests interesting for a totally different reason: They could be essential to the operation of future quantum technologies. In the course of testing this strange, deep feature of nature, people realized these Bell tests could be put to work, says Kaiser.

For example, Googles baby quantum computer, which it plans to test later this year, uses entangled particles to perform computing tasks. Quantum computers could execute certain algorithms much faster because entangled particles can hold and manipulate exponentially more information than regular computer bits. But because entangled particles are so difficult to control, engineers can use Bell tests to verify their particles are actually entangled. Its an elementary test that can show that your quantum logic gate works, Weinfurter says.

Bell tests could also be useful in securing data, says University of Toronto physicist Aephraim Steinberg, who was not involved in the research. Currently, researchers are developing cryptographic protocols based on entangled particles. To send a secure message to somebody, youd encrypt your message using a cryptographic key encoded in entangled quantum particles. Then you send your intended recipient the key. Every now and then, you stop and do a Bell test, says Steinberg. If a hacker tries to intercept the key, or if the key was defective in the first place, you will be able to see it in the Bell tests statistics, and you would know that your encrypted message is no longer secure.

In the near future, Weinfurters group wants to use their experiment to develop a setup that could send entangled particles over long distances for cryptographic purposes. But at the same time, theyll keep performing Bell tests to provebeyond any inkling of a doubtthat entanglement really exists. Because whats the point of developing applications on top of an illusion?

Follow this link:

The Bizarre Quantum Test That Could Keep Your Data Secure - WIRED

May 17, 2017 Experiments at TU Wien (Vienna) -- with a quantum chip, controlling a cloud of atoms. Credit: TU Wien

Quantum field theories are often hard to verify in experiments. Now, there is a new way of putting them to the test. Scientists have created a quantum system consisting of thousands of ultra cold atoms. By keeping them in a magnetic trap on an atom chip, this atom cloud can be used as a 'quantum simulator', which yields new insights into some of the most fundamental questions of physics.

What happened right after the beginning of the universe? How can we understand the structure of quantum materials? How does the Higgs-Mechanism work? Such fundamental questions can only be answered using quantum field theories. These theories do not describe particles independently from each other; all particles are seen as a collective field, permeating the whole universe.

But these theories are often hard to test in an experiment. At the Vienna Center for Quantum Science and Technology (VCQ) at TU Wien, researchers have now demonstrated how quantum field theories can be put to the test in new kinds of experiments. They have created a quantum system consisting of thousands of ultra cold atoms. By keeping them in a magnetic trap on an atom chip, this atom cloud can be used as a "quantum simulator", which yields information about a variety of different physical systems and new insights into some of the most fundamental questions of physics.

Complex Quantum SystemsMore than the Sum of their Parts

"Ultra cold atoms open up a door to recreate and study fundamental quantum processes in the lab", says Professor Jrg Schmiedmayer (VCQ, TU Wien). A characteristic feature of such a system is that its parts cannot be studied independently.

The classical systems we know from daily experience are quite different: The trajectories of the balls on a billiard table can be studied separatelythe balls only interact when they collide.

"In a highly correlated quantum system such as ours, made of thousands of particles, the complexity is so high that a description in terms of its fundamental constituents is mathematically impossible", says Thomas Schweigler, the first author of the paper. "Instead, we describe the system in terms of collective processes in which many particles take partsimilar to waves in a liquid, which are also made up of countless molecules." These collective processes can now be studied in unprecedented detail using the new methods.

Higher Correlations

In high-precision measurements, it turns out that the probability of finding an individual atom is not the same at each point in spaceand there are intriguing relationships between the different probabilities. "When we have a classical gas and we measure two particles at two separate locations, this result does not influence the probability of finding a third particle at a third point in space", says Jrg Schmiedmayer. "But in quantum physics, there are subtle connections between measurements at different points in space. These correlations tell us about the fundamental laws of nature which determine the behaviour of the atom cloud on a quantum level."

"The so-called correlation functions, which are used to mathematically describe these relationships, are an extremely important tool in theoretical physics to characterize quantum systems", says Professor Jrgen Berges (Institute for Theoretical Physics, Heidelberg University). But even though they have played an important part in theoretical physics for a long time, these correlations could hardly be measured in experiments. With the help of the new methods developed at TU Wien, this is now changing: "We can study correlations of different orders - up to the tenth order. This means that we can investigate the relation between simultaneous measurements at ten different points in space", Schmiedmayer explains. "For describing the quantum system, it is very important whether these higher correlations can be represented by correlations of lower orderin this case, they can be neglected at some pointor whether they contain new information."

Quantum Simulators

Using such highly correlated systems like the atom cloud in the magnetic trap, various theories can now be tested in a well-controlled environment. This allows us to gain a deep understanding of the nature of quantum correlations. This is especially important because quantum correlations play a crucial role in many, seemingly unrelated physics questions: Examples are the peculiar behaviour of the young universe right after the big bang, but also for special new materials, such as the so-called topological insulators.

Important information on such physical systems can be gained by recreating similar conditions in a model system, like the atom clouds. This is the basic idea of quantum simulators: Much like computer simulations, which yield data from which we can learn something about the physical world, a quantum simulation can yield results about a different quantum system that cannot be directly accessed in the lab.

The study is published in the journal Nature.

Explore further: Bell correlations measured in half a million atoms

More information: Experimental characterization of a quantum many-body system via higher-order correlations, Nature (2017). nature.com/articles/doi:10.1038/nature22310

Lithium compounds improve plasma performance in fusion devices just as well as pure lithium does, a team of physicists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) has found.

"The best result on dark matter so farand we just got started." This is how scientists behind XENON1T, now the most sensitive dark matter experiment world-wide, commented on their first result from a short 30-day run presented ...

Supersymmetry is an extension to the Standard Model that may explain the origin of dark matter and pave the way to a grand unified theory of nature. For each particle of the Standard Model, supersymmetry introduces an exotic ...

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday electronics like smart phones, computers and TVs.

Osmosis, the fluid phenomenon responsible for countless slug deaths at the hands of mischievous children, is fundamentally important not only to much of biology, but also to engineering and industry. Most simply put, osmosis ...

To capture fast-moving action in a dimly lit environment, a photographer will use the combination of a fast shutter speed and a quick burst of light.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

See more here:

Testing quantum field theory in a quantum simulator - Phys.org - Phys.Org

Forbes

The Marriage Of Einstein's Theory Of Relativity And Quantum Physics Depends On The Pull Of Gravity Forbes As far as I know quantum physics and relativity theory will never get along. Does that mean one of them is basically wrong? originally appeared on Quora: the place to gain and share knowledge, empowering people to learn from others and better ...

Read the original:

The Marriage Of Einstein's Theory Of Relativity And Quantum Physics Depends On The Pull Of Gravity - Forbes

In Brief Scientists at the British University of Columbia have argued that constantly fluctuating space-time is responsible for universal expansion rather than dark energy. This may be an answer to one of the fundamental problems in cosmology. Einstein +Quantum Physics

Scientists at the University of British Columbia have proposed a radical new theory to explain the exponentially increasing size of the universe. Ultimately, it seeks to reconcile two different concepts in physics: Quantum Mechanics and Einsteins Theory of General Relativity. the researchers argue that instead of dark energy causing the universes growth, it could be explainedby constant quantum fluctuations of vacuum energy.

In their work, the researchers argue that, instead of dark energy causing the universes growth, it could be explainedby constant quantum fluctuations of vacuum energy. The paper claims if their findings are true that the old cosmological constant problem would be resolved. The press release notes the potentially transformative nature of the work: Their calculations provide a completely different physical picture of the universe.

Similarly, Bill Unruh, the physics and astronomy professor who supervised P.H.D student Qingdi Wangs work,stated thatthe research offers an entirely new take on old problems: This is a new idea in a field where there hasnt been a lot of new ideas that try to address this issue. In the end, their calculations provide a fundamentally different picture of the universe: one in which space-time is constantly moving, fluctuating between contraction and expansion.Its the small net effect towards expansion, though, that drives the expansion of the universe.

Unruh uses the sea as an analogy to explain why we cannot feel the effects: Its similar to the waves we see on the ocean [] They are not affected by the intense dance of the individual atoms that make up the water on which those waves ride.

Previous beliefhas held that the universe is expanding steadily due to dark energy pushing other matter further and further away. When we apply quantum theories to vacuum energy, it results in an increasing density which could in turn result in universal explosion due to the gravitational effect of the density.

The discovery that the universe is expanding was made simultaneously by two independent teams in 1998: Supernova Cosmology Project and the High-Z Supernova Search Team. Three members of the two teams have since won Nobel prizes for their work, which measured light using standard candles. Since that discovery was made, scientists have tried to work outexactly what this energy is thats driving the cosmos apart.

Despite the fact that it has been a compelling mystery for decades, there havent been that many theoriesposed. So, while the work of Wang and Unruh may not provide the ultimate answer, they present a new, potential solution to one of the most fundamental problems in cosmology.

Editors note: This article has been updated. A previous version mistakenly referred to dark energy as dark matter.

Read more here:

New Research May Reconcile General Relativity and Quantum Mechanics - Futurism

By Josh Mitteldorf

How surprised should we be if 4 billion years of evolution have taught the living cell to exploit quantum mechanics in ways that human physicists have not yet discovered? Science has made great progress in the last century via reductionism, understanding the parts and building up to an understanding of the whole. The idea of a direct link between micro-world of quantum mechanics and the complexity of life could disrupt that paradigm.

From ancient times, it was obvious to people the world over that life played by different rules. Flowers and frogs could do things that rocks and babbling brooks could never do. Great scientists through Newton and Faraday saw no conflict between their spiritual beliefs and the laws of nature they were discovering. Then, in the 19th Century, organic chemistry was developed, and cells could be viewed through a microscope. Some of the behavior of living things began to find explanations in terms of physics and chemistry. One after another of the abilities of living cells were explained with the same laws that apply to non-living matter. Science and philosophy came to make a bold extrapolation: There is no fundamental difference. Living and non-living matter obey the same laws, and the apparent difference between living and non-living systems is due to complexity only.

This possibility became a presumption and then a dogma. Worse, the laws that governed life were presumed to be physics that humans have presently mastered and understood. Scientific consensus lined up against the idea that life may know something we dont know.

Of course, biology continues to hold many mysteries for us: Animal navigation and extraordinary knowing; the remarkable efficiency of evolution, and the related problem of the origin of life; why should microwaves cause cancer? why, indeed, should weak radio waves have any interaction with living tissue? How can biological enzymes be so much more specific than engineered catalysts, and why are they less effective in a petri dish than in a living cell?

In the process of attacking these open questions of biology, will we discover new physics? To date, only a handful of quantum biologists are asking such questions.

The first and most famous proponent of quantum biology was Erwin Schrdinger, a founding father of quantum physics. In the 1930s, he wrote two monographs [republished in one volume] about physics and life. The first one prefigured by more than a decade Crick and Watsons discovery of the structure of DNA. The second hypothesized that consciousness has an elemental role in the fabric of physics. Though this latter idea sounds mystical and vaguely unscientific to biologists, it is taken seriously by physicists because the postulates of quantum mechanics require* a subjective observer, and reality is not objective or observer-independent, but arises from the interaction between the observer and his representation of a physical system. A world without objective reality? This sounds too fantastical to take seriously, and most scientists dont.

Since Schrdinger, there have been reports of experimental results that would seem to support his conjectures about the quantum basis of life, but these have remained on the edge of science, subjected to a rigid skepticism because they would seem to require such a radical re-conception of the reductionist view of science. In the standard scientific picture, physics explains atoms and molecules; atomic physics is the explanation for chemistry; and chemistry explains the behavior of biological systems. The alternative is that the loop may be closed: biology is necessary to explain fundamental physics. (Theres a joke** with the punch line, God is a biologist.)

Aside from the quantum mechanical observer, another reason to take this idea seriously is a series of remarkable coincidences first noted by astrophysicists: The recipe for our universe contains six fundamental but arbitrary ratiosthings like the ratio of the electron to proton mass and the ratio of the electric force to the gravitational force. These ratios give the appearance of being fine-tuned to make life possible. If any of them were just a wee bit different, we would live in a universe that was very much less interesting than the one we do live in. (For example a universe in which the only chemical element is hydrogen, or a universe in which intergalactic gas remains spread thin and never congeals into stars and planets.)

What is the significance of the fact that these arbitrary ratios are fine-tuned to make life possible? One explanation would be that consciousness played a founding role, and is in some way responsible for the world we see. The alternative is that there are many universes, (billions and billions) and almost all of them harbor no life, because life is not possible there, so of course we find ourselves in one of the exceedingly rare universes that is capable of supporting life.

Aside from these broad, philosophical arguments, there are two direct observations opening the door to quantum biology. Photosynthesis and magnetic sensors in birds are made possible by quantum superpositions within single molecules. A more expansive view of quantum biology is that life depends on quantum tricks that allow micron-sized systems to explore many possibilities simultaneously, and enable single molecules to flip switches for entire cells. These are considered radical ideas, outside the mainstream of science, but perhaps they provide a fertile hypothesis for exploring many mysteries of biology.

Stunning reports of the quantum influence of living systems have been dismissed as not worthy of review or replication, because we know as a matter of theory that they must be mistaken. Robert Jahn, while Dean of the Princeton University School of Engineering, began an investigation of ways in which living systems (including humans) can affect quantum noise in a resistor [book]. Though his experiments were expertly and meticulously documented, they were never permitted publication in journals of physics, and in fact Dr Jahns reputation and career suffered just for having undertaken such experiments.

There is a line of experimentation from Russia reporting that plants and even bacteria are able to transmute chemical elements, a process which humans know how to do only with high-energy nuclear physics [book]. These experiments have never been replicated in the West, and the implications would be revolutionary if confirmed.

Roger Penrose, one of the most brilliant and original minds in mathematical physics, has been speculating on quantum theories of consciousness for thirty years, making specific and testable proposals. It is scandalous that his work is dismissed as crackpot by people who dont understand it. There is a mainstream view that consciousness arises from computation, and that digital computers have, in principle, everything necessary to qualify as conscious, living beings when we learn how to program them a bit better. Though this hypothesis is far from being a proven fact of science, challenging the dogma can be hazardous to a scientific career.

Stuart Kauffman is another expansive thinker who has investigated the connections between quantum mechanics, biology and consciousness. He notes that many proteins, including about half of all neurotransmitters, are in a state of quantum criticality, which means they are poised on a knife edge, easily nudged between two configurations. Why would this be true? In designing a classical machine (for example a tiny transistor, etched on a microchip), human engineers make sure that the systems performance is reliable by making it just large enough that quantum fluctuations cannot affect its behavior. There are plenty of biological systems that are also designed to be stable in this way; the DNA molecule, for example, stores information reliably over long periods of time. But natural selection seems to have gone out of her way to use neurotransmitters that are unreliable. Their behavior (and our thinking) are affected by quantum events at the smallest level. This could be a useful feature of the brain if quantum events in living systems are not random, but are guided by a larger coherence, or by consciousness as an entity, or maybe these two are different aspects of the same thing.

In 2002, a molecular geneticist from University of Surrey outlined a bold theory of quantum evolution based on extrapoloation of a well-established but paradoxical phenomenon. In the Quantum Zeno Effect, continuous observation of one quantum variable prevents a system from evolving. (Watched water never boils.) It is theoretically possible, in this way, to prevent a radioactive nucleus from decaying. The Inverse Quantum Zeno Effect is yet stranger: By very gradually changing the quantum variable under observation, it is possible to guide a quantum system efficiently from one state to another. In a simple demonstration (try this at home!), a series of rotated polarized filters can nudge vertically polarized light around until it becomes horizontally polarized, though the overlap between the initial and final wave functions is zero. In this book, Johnjoe McFadden speculated that biological evolution might be directed toward states of higher fitness by a biological version of the Inverse Zeno Effect. Fifteen years later, only a handful of scientists around the world are discussing and developing these ideas. We are so busy working out the details of our existing framework (and writing grant proposals to compete for next years funding) that we have no time to consider speculations outside the box.

Mcfadden stopped short of proposing an observer within the living cell that is driving its evolution, a deus ex machina, but connection to Penroses work presents a tantalizing possibility. Perhaps the contentious observer problem of quantum mechanics is essentially related to free will, awareness and the sense of self; perhaps the quantum observer within is what separates living from non-living things, and is the source of the characteristic behaviors that strike us as goal-oriented.

These intriguing ideas touch our foundational sense of who we are and the nature of the world in which we live, but the enterprise of science today is not well adapted to address them. Funding is risk-aversea sound basis for business decisions, but a disaster for the healthy practice of basic science. Hypotheses about quantum biology are easily dismissed as crackpot, and indeed most are likely not to pan out. But you have to kiss many a frog before you find your prince. If we are ever to address these foundational questions, wethe community of scientistswill have to be willing to consider and to test a great number of crazy ideas along the way.

We know the quantum world primarily from single-particle systems. All of atomic physics, chemical bonds, orbitals etc. is modeled from equations of the hydrogen atom, because for more than one electron, quantum mechanical equations are impossible to solve. Quantum physics of many entangled particle is notoriously intractable to computation, so we have only semi-empirical theories of chemistry and solid state physics. With quantum symmetries, we can explain simple, uniform orderfor example, lasers and crystals. But theory suggests the possibility of a single quantum state that comprises many atoms in a complex array; indeed, a system may be in a superposition of several such states simultaneously. We know nothing of such systems, or what properties they might evince; that is, we know how to write down the equations for such systems but to solve the equations is far beyond the capability of any computer we know how to build. Quantum mechanics of complex systems remains an experimental science, and evolution has had time to perform a great many more experiments than have humans.

* There is an alternative formulation of quantum mechanics where observers are not outside of quantum physics, but this formulation carries the baggage of a truly gigantuous number of extra universes, all them completely unobservable. It is called the Many Worlds Interpretation.

** Escalating reductionism: Biologists think theyre chemists, chemists think theyre physicists, physicists think theyre mathematicians. Of course, mathematicians think theyre God, but what they dont realize is that God is a biologist.

Read more from the original source:

Quantum Biology and the Frog Prince - ScienceBlog.com (blog)